I'm definitely skeptical of claims that UFOs are spaceships piloted by extraterrestrial beings. Even if aliens had Star Trek warp drives, they would have to search the universe for billions of years before they stumbled upon us. Our TV transmissions have only reached about 50 light years into space, and there's no indication of extra-solar planets that close. However, it's a certainty that people sometimes see, and photograph, flying objects that seem to defy explanation.